Question

I’m creating a backup system, where backups will be generated automaticly, so I will be storing backups on a different server, however when I want to download them, I want the link to be a one time link, this isn’t hard to make, however to make this secure I was thinking about storing the files so their not accesible via http on the other server.

So what I would do is connet via ftp, download the file to the main server, then present it for download and deleteit, however this will take a long time if the backup is large, is there a way to stream it from FTP without showing the person who is downloadiong the actual location and not store it on the server?

Answer 1

Here is a very basic example using cURL. It specifies a read callback which will be called when data is available to be read from FTP, and outputs the data to the browser to serve a simultaneous download to the client while the FTP transaction is taking place with the backup server.

This is a very basic exmaple which you can expand on.

<?php

// ftp URL to file
$url = 'ftp://ftp.mozilla.org/pub/firefox/nightly/latest-firefox-3.6.x/firefox-3.6.29pre.en-US.linux-i686.tar.bz2';

// init curl session with FTP address
$ch = curl_init($url);

// specify a callback function for reading data
curl_setopt($ch, CURLOPT_READFUNCTION, 'readCallback');

// send download headers for client
header('Content-type: application/octet-stream');
header('Content-Disposition: attachment; filename="backup.tar.bz2"');

// execute request, our read callback will be called when data is available
curl_exec($ch);


// read callback function, takes 3 params, the curl handle, the stream to read from and the maximum number of bytes to read    
function readCallback($curl, $stream, $maxRead)
{
    // read the data from the ftp stream
    $read = fgets($stream, $maxRead);

    // echo the contents just read to the client which contributes to their total download
    echo $read;

    // return the read data so the function continues to operate
    return $read;
}

See curl_setopt() for more info on the CURLOPT_READFUNCTION option.